Dispersant in cement formulations for oil and gas wells

ABSTRACT

Cement slurries, cured cements, and methods of making cured cement and methods of using cement slurries are provided. The cement slurries have, among other attributes, improved rheology, such as improved flowability and pumpability and may be used, for instance, in the oil and gas drilling industry. The cement slurry contains water, a cement precursor material and a surfactant having the formula R—(OC 2 H 4 ) x —OH where R is a hydrocarbyl group comprising from 10 to 20 carbon atoms and x is an integer from 1 and 10. The cured cement have improved strength and density properties due to reduced fluid loss and even placement during curing. The cured cement contains a surfactant having the formula R—(OC 2 H 4 ) x —OH where R is a hydrocarbyl group comprising from 10 to 20 carbon atoms and x is an integer from 1 and 10.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/002,672 filed Jun. 7, 2018, which claimspriority to U.S. patent application Ser. No. 15/628,892 filed Jun. 21,2017, which claims priority to U.S. Provisional Patent Application Ser.No. 62/454,189 filed Feb. 3, 2017 and U.S. Provisional PatentApplication Ser. No. 62/454,192 filed Feb. 3, 2017, which areincorporated by reference herein in their entirety.

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to cementslurries and methods of making and using cement slurries and to curedcements and methods of making cured cement. Specifically, embodiments ofthe present disclosure relate to cement slurries and cured cements thathave at least one surfactant and methods of making and using cementslurries and cured cements having a surfactant.

BACKGROUND

Cement slurries are used in the oil and gas industries, such as forcementing in oil and gas wells. Primary, remedial, squeeze, and plugcementing techniques can be used, for instance, to place cement sheathsin an annulus between casing and well formations, for well repairs, wellstability, for well abandonment (sealing an old well to eliminate safetyhazards), and many other applications. These cement slurries must beable to consistently perform over a wide range of temperatures andconditions, as oil and gas wells can be located in a multitude ofdiverse locations. For example, a cement slurry may be used inconditions of from below 0° in freezing permafrost zones, and intemperatures exceeding 400° C. in geothermal wells and, as such, must beable to properly set under an assortment of conditions.

Proper hardening of a cement slurry can be vital to the strength andperformance properties of the cured cement composition. However,conventional cement solutions have poor flowability due to the viscousnature of the slurry, creating concerns when handling or pumping thecement, as uniform placement of the slurry can be quite difficult.Moreover, cement slurries are often incompatible with other fluids thatmay be present in the casing or the wellbore wall, such as drillingfluids, and prolonged contact could cause the cement slurry to gel,preventing proper placement and removal of the cement. Additionalproblems are encountered when curing a cement slurry into a curedcement. Cement slurries often cure through water-based reactions and,thus, too much or too little water loss can negatively impact thehardening process. Water may be lost or gained due to inclement weather,the conditions of the soil surrounding the well, or a multitude of otherfactors.

SUMMARY

Accordingly, there is an ongoing need for cement slurries having goodflowability and pumpability with improved fluid loss control and forcured cement compositions that have cured uniformly without unwantedadditional additives or artificially created conditions. The presentembodiments address these needs by providing cement slurries and methodsof making and using cement slurries that have improved rheology andfluid loss control, and cured cements and methods of making cured cementthat cures uniformly with improved hardness and good wettability.

In one embodiment, cement slurries are provided, which contain water, acement precursor material and a surfactant having the formulaR—(OC₂H₄)_(x)—OH, where R is a hydrocarbyl group comprising from 10 to20 carbon atoms and x is an integer from 1 and 10. The surfactant mayhave a hydrophilic-lipophilic balance (HLB) of from 12 to 13.5.

In another embodiment, cured cements are provided, in which the curedcement contains a surfactant having the formula R—(OC₂H₄)_(x)—OH, whereR is a hydrocarbyl group comprising from 10 to 20 carbon atoms and x isan integer from 1 and 10. The surfactant may have an HLB of from 12 to13.5.

In another embodiment, methods of producing a cured cement are provided.The methods include mixing water with a cement precursor material and asurfactant having the formula R—(OC₂H₄)_(x)—OH, where R is a hydrocarbylgroup comprising from 10 to 20 carbon atoms and x is an integer from 1and 10. The surfactant may have an HLB of from 12 to 13.5. The methodfurther includes curing the cement slurry into a cured cement.

In another embodiment, methods of cementing a casing a wellbore areprovided. The methods include pumping a cement slurry into an annulusbetween a casing and a wellbore. The cement slurry includes water, acement precursor material and a surfactant having the formulaR—(OC₂H₄)_(x)—OH, where R is a hydrocarbyl group comprising from 10 to20 carbon atoms and x is an integer from 1 and 10. The surfactant mayhave an HLB of from 12 to 13.5. The method further includes curing thecement slurry to cement the casing in the wellbore.

Additional features and advantages of the described embodiments will beset forth in the detailed description which follows, and in part will bereadily apparent to those skilled in the art from that description orrecognized by practicing the described embodiments, including thedetailed description which follows as well as the claims.

DETAILED DESCRIPTION

Embodiments of the present disclosure relate to cement slurries andmethods of making and using cement slurries that have, among otherattributes, improved rheology, such as improved flowability andpumpability. As used throughout the disclosure, “cement slurry” refersto a composition comprising a cement precursor that is mixed with atleast water to form cement. The cement slurry may contain calcinedalumina (Al₂O₃), silica (SiO₂), calcium oxide (CaO, also known as lime),iron oxide (FeO), magnesium oxide (MgO), clay, sand, gravel, andmixtures of these. Embodiments of the present disclosure also relate tomethods of producing and using cement slurries, in some particularembodiments, for use in the oil and gas industries. Still furtherembodiments of the present disclosure relate to cured cements andmethods of producing cured cements. As used throughout this disclosure,“cured cement” refers to the set, hardened reaction product of thecomponents of a cement slurry.

As a non-limiting example, the cement slurries and cured cementcompositions of the present disclosure may be used in the oil and gasdrilling industries, such as for cementing in oil and gas wells. Oil andgas wells may be formed in subterranean portions of the Earth, sometimesreferred to as subterranean geological formations. The wellbore mayserve to connect natural resources, such as petrochemical products, to aground level surface. In some embodiments, a wellbore may be formed inthe geological formation, which may be formed by a drilling procedure.To drill a subterranean well or wellbore, a drill string including adrill bit and drill collars to weight the drill bit is inserted into apredrilled hole and rotated to cut into the rock at the bottom of thehole, producing rock cuttings. Commonly, drilling fluid, known as“drilling mud,” may be utilized during the drilling process. To removethe rock cuttings from the bottom of the wellbore, drilling fluid ispumped down through the drill string to the drill bit. The drillingfluid cools the drill bit and lifts the rock cuttings away from thedrill bit and carries the rock cuttings upwards as the drilling fluid isrecirculated back to the surface.

In some instances, a casing may be inserted into the wellbore. Thecasing may be a pipe or other tubular structure which has a diameterless than that of the wellbore. Generally, the casing may be loweredinto the wellbore such that the bottom of the casing reaches to a regionnear the bottom of the wellbore. In some embodiments, the casing may becemented by inserting a cement slurry into the annulus region betweenthe outer edge of the casing and the edge of the wellbore (the surfaceof the geological formation). The cement slurry may be inserted into theannular region by pumping the cement slurry into the interior portion ofthe casing, to the bottom of the casing, around the bottom of thecasing, into the annular region, or a combination of some or all ofthese. The cement slurry may displace the drilling fluid, pushing it tothe top of the well. In some embodiments, a spacer fluid may be used asa buffer between the cement slurry and the drilling fluid by displacingand removing the drilling fluid before the cement slurry is pumped intothe well to prevent contact between the drilling fluid and the cementslurry. Following the insertion of an appropriate amount of cementslurry into the interior region of the casing, in some embodiments, adisplacement fluid may be utilized to push the cement slurry out of theinterior region of the casing and into the annular region. Thisdisplacement may cause the entirety of the spacer fluid and drillingfluid to be removed from the annular region, out the top of thewellbore. The cement slurry may then be cured or otherwise allowed toharden.

To ensure the stability and safety of a well, it is important that thecement slurry properly harden into cured cement. If the cement slurry isnot evenly placed or fluid is lost from the cement slurry before curing,the cement slurry may not evenly harden into a cured cement. Therefore,the viscosity and flowability of a cement slurry is important to ensureproper placement. Similarly, reducing fluid loss from the cement slurryensures uniform hardening, as curing often involves water-basedreactions with the cement slurry. Too much or too little water affectsthe hardness and, thus, the quality of the cured cement produced.

A number of conditions may impact the fluid loss of a cement slurry. Forinstance, water may be drawn from the slurry into the permeableformation, particularly if pumping ceases and the slurry becomes staticwithout hardening. Water may also be lost due to displacement as thecement slurry is passed through constrictions, such as the tightclearance between a casing and an annulus, which may “squeeze” waterfrom the slurry. Adverse weather and soil conditions may additionalimpact the amount of water present in the cement slurry. As such,control of fluid loss of the cement slurry may allow for a more uniformand stronger cured cement.

The present disclosure provides cement slurries which may have, amongother attributes, improved rheology and reduced fluid loss to addressthese concerns. The cement slurry of the present disclosure includeswater, a cement precursor material, and a surfactant. Without beingbound by any particular theory, use of the surfactant along with thecement precursor material in some embodiments may provide reducedviscosity of the cement slurry to allow for easier processing,flowability, and handling of the cement slurry in various applications.In some embodiments, use of the surfactant along with the cementprecursor material may provide reduced water content in the cementslurry and, in some embodiments, may reduce the friction pressure of thecement slurry to aid in drying and curing the cement slurry. In someembodiments, use of the surfactant along with the cement precursormaterial may additionally improve efficiency and performance of otheroptional additives, such as fluid loss additives. Moreover, dispersingthe cement and reducing the friction between the cement and water willreduce the pumping pressure needed to pump and place cement into thewell.

The cement precursor material may be any suitable material which, whenmixed with water, can be cured into a cement. The cement precursormaterial may be hydraulic or non-hydraulic. A hydraulic cement precursormaterial refers to a mixture of limestone, clay and gypsum burnedtogether under extreme temperatures that may begin to harden instantlyor within a few minutes while in contact with water. A non-hydrauliccement precursor material refers to a mixture of lime, gypsum, plastersand oxychloride. A non-hydraulic cement precursor may take longer toharden or may require drying conditions for proper strengthening, butoften is more economically feasible. A hydraulic or non-hydraulic cementprecursor material may be chosen based on the desired application of thecement slurry of the present disclosure. In some embodiments, the cementprecursor material may be Portland cement precursor, for example, ClassG Portland Cement. Portland cement precursor is a hydraulic cementprecursor (cement precursor material that not only hardens by reactingwith water but also forms a water-resistant product) produced bypulverizing clinkers, which contain hydraulic calcium silicates and oneor more of the forms of calcium sulphate as an inter-ground addition.

The cement precursor material may include one or more of calciumhydroxide, silicates, oxides, belite (Ca₂SiO₅), alite (Ca₃SiO₄),tricalcium aluminate (Ca₃Al₂O₆), tetracalcium aluminoferrite(Ca₄Al₂Fe₂O₁₀), brownmillerite (4CaO.Al₂O₃.Fe₂O₃), gypsum (CaSO₄.2H₂O)sodium oxide, potassium oxide, limestone, lime (calcium oxide),hexavalent chromium, calcium aluminate, silica sand, silica flour,hematite, manganese tetroxide, other similar compounds, and combinationsof these. The cement precursor material may include Portland cement,siliceous fly ash, calcareous fly ash, slag cement, silica fume, anyknown cement precursor material or combinations of any of these.

In some embodiments, the cement slurry may contain from 0.001 to 10%BWOC (by weight of cement), or less than 1% BWOC.

Water may be added to the cement precursor material to produce theslurry. The water may be distilled water, deionized water, or tap water.In some embodiments, the water may contain additives or contaminants.For instance, the water may include freshwater or seawater, natural orsynthetic brine, or salt water. In some embodiments, salt or otherorganic compounds may be incorporated into the water to control certainproperties of the water, and thus the cement slurry, such as density.Without being bound by any particular theory, increasing the saturationof water by increasing the salt concentration or the level of otherorganic compounds in the water may increase the density of the water,and thus, the cement slurry. Suitable salts may include, but are notlimited to, alkali metal chlorides, hydroxides, or carboxylates. In someembodiments, suitable salts may include sodium, calcium, cesium, zinc,aluminum, magnesium, potassium, strontium, silicon, lithium, chlorides,bromides, carbonates, iodides, chlorates, bromates, formates, nitrates,sulfates, phosphates, oxides, fluorides, and combinations of these.

In some embodiments, the cement slurry may contain from 10 wt. % to 70wt. % water based on the total weight of the cement slurry. In someembodiments, the cement slurry may contain from 10 wt. % to 40 wt. %,from about 10 wt. % 30 wt. %, 10 wt. % to 20 wt. %, from 20 wt. % to 40wt. %, or from 20 wt. % to 30 wt. % of water. The cement slurry maycontain from 20 wt. % to 40 wt. %, or from 25 wt. % to 35 wt. %, such as30 wt. % of water based on the total weight of the cement slurry.

Along with the cement precursor material and water, the cement slurrymay include at least one surfactant. According to one or moreembodiments, the surfactant may have the chemical structure of Formula(I):

R—(OC₂H₄)_(x)—OH  Formula (I)

In Formula (I), R is a hydrocarbyl group having from 10 to 20 carbonatoms and x is an integer from 1 to 10. As used in this disclosure, a“hydrocarbyl group” refers to a chemical group consisting of carbon andhydrogen. Typically, a hydrocarbyl group may be analogous to ahydrocarbon molecule with a single missing hydrogen (where thehydrocarbyl group is connected to another chemical group). Thehydrocarbyl group may contain saturated or unsaturated carbon atoms inany arrangement, including straight (linear), branched, aromatic, orcombinations of any of these configurations. The hydrocarbyl R group insome embodiments may be an alkyl (—CH₃), alkenyl (—CH═CH₂), alkynyl(—C≡CH), or cyclic hydrocarbyl group, such as a phenyl group, which maybe attached to a hydrocarbyl chain.

In one or more embodiments, R may include from 10 to 20 carbons, such asfrom 10 to 18 carbons, from 10 to 16 carbons, from 10 to 14 carbons, orfrom 10 to 12 carbons. R may have from 11 to 20 carbons, from 13 to 20carbons, from 15 to 20 carbons, from 17 to 20 carbons, from 10 to 15carbons, or from 12 to 15 carbons, or from 12 to 14 carbons. In someembodiments, R may have 12 carbons, 13 carbons, 14 carbons or 15carbons. In some particular embodiments, R may have 13 carbons, and, insome embodiments, R may be C₁₃H₂₇ (iso tridecyl).

In Formula (I), x is an integer between 1 and 10. In some embodiments, xmay be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. In some embodiments, x may bean integer from 5 to 10, from 5 and 9, from 7 to 10, or from 7 to 9. Insome embodiments, x may be an integer greater than or equal to 5, suchas an integer greater than or equal to 7, or greater than or equal to 8.

The surfactant may be amphiphilic, meaning that it has a hydrophobictail (the non-polar R group) and a hydrophilic head (the polar —OHgroups from ethylene oxide and the alcohol group) that may lower thesurface tension between two liquids or between a liquid. In someembodiments, the surfactant may have a hydrophilic-lipophilic balance(HLB) of from 11 to 13. Without being bound by any particular theory,the HLB of the compound is the measure of the degree to which it ishydrophilic or lipophilic, which may be determined by calculating valuesfor the regions of the molecules in accordance with the Griffin Methodin accordance with Equation 1:

$\begin{matrix}{{HLB} = {20 \times \frac{M_{h}}{M}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In Equation 1, M_(h) is the molecular mass of the hydrophilic portion ofthe molecule and M is the molecular mass of the entire molecule. Theresulting HLB value gives a result on a scale of from 0 to 20 in which avalue of 0 indicates to a completely hydrophobic/lipophilic molecule anda value of 20 corresponds to a completely hydrophilic/lipophobicmolecule. Generally, a molecule having an HLB of less than 10 islipid-soluble (and thus water-insoluble) and a molecule having an HLB ofgreater than 10 is water-soluble (and thus lipid-insoluble). In someembodiments, the surfactant may have an HLB of from 12 to 13.5. Thesurfactant may have an HLB of from 12 to 13, from 12.5 to 13.5, from12.25 to 13.5, from 12.25 to 13, from 12.25 to 13.25, or from 12.25 to12.75. In some embodiments, the surfactant may have an HLB of 12, 12.5,12.75, 13, 13.25, or 13.5. This HLB value may indicate that thesurfactant has both hydrophilic and lipophilic affinities (as thesurfactant is amphiphilic) but has a slightly greater tendency towardsbeing hydrophilic/lipophobic, and thus, may be water-soluble.

The cement slurry may contain from 0.1 to 10% BWOC of the surfactantbased on the total weight of the cement slurry. For instance, the cementslurry may contain from 0.1 to 8% BWOC of the surfactant, from 0.1 to 5%BWOC of the surfactant, or from 0.1 to 3% BWOC of the surfactant. Thecement slurry may contain from 1 to 10% BWOC, from 1 to 8% BWOC, from 1to 5% BWOC, or from 1 to 3% BWOC of the surfactant. In some embodiments,the cement slurry may contain from 3 to 5% BWOC, from 3 to 8% BWOC, from3 to 10, or from 5 to 10% BWOC of the surfactant.

The surfactant may be a reaction product of a fatty alcohol ethoxylatedwith ethylene oxide. As used throughout the disclosure, a fatty alcoholrefers to a compound having a hydroxyl (—OH) group and at least onealkyl chain (—R) group. The ethoxylated alcohol compound may be made byreacting a fatty alcohol with ethylene oxide. The ethoxylation reactionin some embodiments may be conducted at an elevated temperature and inthe presence of an anionic catalyst, such as potassium hydroxide (KOH),for example. The ethoxylation reaction may proceed according to Equation2:

$\begin{matrix}{{R{OH}} + {{xC}_{2}H_{4}{O\overset{KOH}{}{R\left( {{OCH}_{2}{CH}_{2}} \right)}_{X}}{OH}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

The fatty alcohols used as the reactant in Equation 2 to make theethoxylated alcohol compound could include any alcohols having formulaR—OH, where R is a saturated or unsaturated, linear, or branchedhydrocarbyl group having from 10 to 20 carbon atoms, from 10 to 16carbon atoms, or from 12 to 14 carbon atoms. In some embodiments, R maybe a saturated linear hydrocarbyl group. Alternatively, the fattyalcohol may include R that is a branched hydrocarbyl group.

In some embodiments, the R—OH group of the surfactant may be anaturally-derived or synthetically-derived fatty alcohol. Non-limitingexamples of suitable fatty alcohols may include, but are not limited tocapryl alcohol, perlargonic alcohol, decanol (decyl alcohol), undecanol,dodecanol (lauryl alcohol), tridecanol (tridecyl alcohol), myristylalcohol (1-tetradec anol), pentadecanol (pentadecyl alcohol), cetylalcohol, palmitoleyl alcohol, heptadecanol (heptadecyl alcohol) stearylalcohol, nonadecyl alcohol, arachidyl alcohol, other naturally-occurringfatty alcohols, other synthetic fatty alcohols, or combinations of anyof these. The fatty alcohol may be a naturally occurring fatty alcohol,such as a fatty alcohol obtained from natural sources, such as animalfats or vegetable oils, like coconut oil. The fatty alcohol may be ahydrogenated naturally-occurring unsaturated fatty alcohol.Alternatively, the fatty alcohol may be a synthetic fatty alcohol, suchas those obtained from a petroleum source through one or more synthesisreactions. For example, the fatty alcohol may be produced through theoligomerization of ethylene derived from a petroleum source or throughthe hydroformylation of alkenes followed by hydrogenation of thehydroformylation reaction product. This synthetic fatty alcohol maydemonstrate improved performance at high temperature and higher salinitylevels.

As shown in Equation 2, the reaction product may have the generalchemical formula R—(OCH₂CH₂)_(x)—OH, where R is a saturated orunsaturated, linear or branched hydrocarbyl group having from 10 to 20carbon atoms. According to some embodiments, the R group may be aniso-tridecyl group (—C₁₃H₂₇), as depicted in Chemical Structure A. Itshould be understood that Chemical Structure A depicts one possibleembodiment of the surfactant of Formula (I) in which the R group is aiso-tridecyl group, which is used as a non-limiting example. In someembodiments, Chemical Structure (A) may have 8 ethoxy groups (that is, xequals 8 in Chemical Structure (A)) such that the surfactant is atridecyl alcohol ethyoxylate with an 8:1 molar ratio of ethylene oxidecondensate to branched isotridecyl alcohol having the chemical formulaC₁₃H₂₇—(OCH₂CH₂)₈—OH.

Generally, an x:1 molar ratio of the fatty alcohol to the ethylene oxidemay be utilized to control the level of ethoxylation in Equation 2. Insome embodiments, x may be from 1 to 10, such as 1, 2, 3, 4, 5, 6, 7, 8,9, or 10. In some embodiments, the surfactant may be the reactionproduct of fatty alcohol ethoxylated with ethylene oxide at an 8:1 molarratio of fatty alcohol to ethylene oxide. In some particularembodiments, the surfactant may be a synthetic alcohol oxylate and maybe an ethylene oxide condensate of isotridecyl alcohol. The surfactantmay be produced by an 8:1 molar ratio of ethylene oxide to isotridecylalcohol. In some particular embodiments, the surfactant may be producedby an 8:1 molar ratio of ethylene oxide condensate to synthetic branchedisotridecyl alcohol.

In some embodiments, the cement slurry may contain at least one additiveother than the surfactant. The one or more additives may be anyadditives known to be suitable for cement slurries. As non-limitingexamples, suitable additives may include accelerators, retarders,extenders, weighting agents, fluid loss control agents, lost circulationcontrol agents, other surfactants, antifoaming agents, specialtyadditives such as elastomers or fibers, and combinations of these.

In some embodiments, the cement slurry may contain from 0.1 to 10% BWOCof the one or more additives based on the total weight of the cementslurry. For instance, the cement slurry may contain from 0.1 to 8% BWOCof the one or more additives, from 0.1 to 5% BWOC of the one or moreadditives, or from 0.1 to 3% BWOC of the one or more additives. Thecement slurry may contain from 1 to 10% BWOC of the one or moreadditives, from 1 to 8% BWOC, from 1 to 5% BWOC, or from 1 to 3% BWOC ofthe one or more additives. In some embodiments, the cement slurry maycontain from 3 to 5% BWOC, from 3 to 8% BWOC, from 3 to 10% BWOC, orfrom 5 to 10% BWOC of the one or more additives.

In some embodiments, the one or more additives may include a dispersantcontaining one or more anionic groups. For instance, the dispersant mayinclude synthetic sulfonated polymers, lignosulfonates with carboxylategroups, organic acids, hydroxylated sugars, other anionic groups, orcombinations of any of these. Without being bound by any particulartheory, in some embodiments, the anionic groups on the dispersant may beadsorbed on the surface of the cement particles to impart a negativecharge to the cement slurry. The electrostatic repulsion of thenegatively charged cement particles may allow the cement slurry to bedispersed and more fluid-like, improving flowability. This may allow forone or more of turbulence at lower pump rates, reduction of frictionpressure when pumping, reduction of water content, and improvement ofthe performance of fluid loss additives.

In some embodiments, the one or more additives may alternatively oradditionally include a fluid loss additive. In some embodiments, thecement fluid loss additive may include non-ionic cellulose derivatives.In some embodiments, the cement fluid loss additive may behydroxyethylcellulose (HEC). In other embodiments, the fluid lossadditive may be a non-ionic synthetic polymer (for example, polyvinylalcohol or polyethyleneimine). In some embodiments, the fluid lossadditive may be an anionic synthetic polymer, such as2-acrylamido-2-methylpropane sulfonic acid (AMPS) or AMPS-copolymers,including lattices of AMPS-copolymers. In some embodiments, the fluidloss additive may include bentonite, which may additionally viscosifythe cement slurry and may, in some embodiments, cause retardationeffects. Without being bound by any particular theory, the surfactantmay reduce the surface tension of the aqueous phase of the cementslurry, thus reducing the fluid lost by the slurry. Additionally, thecarboxylic acid may further reduce the fluid loss of the cement slurryby plugging the pores of the cement filter cake, minimizing space forthe water or other fluids to escape from the cement.

In some embodiments, the fluid loss additive may contain a carboxylicfatty acid having from 16 to 18 carbon atoms, which may be used incombination with the surfactant to reduce fluid loss in the cementslurry. The carboxylic fatty acid includes any acids having formula ROOHin which R is a saturated or unsaturated, linear, or branchedhydrocarbyl group having from 16 to 18 carbons, such as a hydrocarbylgroup having 16 carbons, 17 carbons, or 18 carbons. Examples of suitablecarboxylic fatty acids include palmitic acid, palmitoleic acid, vaccenicacid, oleic acid, elaidic acid, linoleic acid, α-linolenic acid,γ-linolenic acid, stearidonic acid, and combinations thereof. Thesurfactant may be in accordance with any of the embodiments previouslydescribed. In some specific embodiments, the fluid loss additive maycontain a combination of an ethylene oxide condensate of branchedisotridecyl alcohol with a fatty acid having from 16 to 18 carbon atomsin the hydrocarbyl group.

In some embodiments, the cement slurry may contain from 0.1% BWOC to 10%BWOC of one or more fluid loss additives, the one or more dispersants,or both. The cement slurry may contain from 0.02 to 90 lb/bbl of thefluid loss additives, the one or more dispersants, or both based on thetotal weight of the cement slurry. For instance, the cement slurry maycontain from 0.1 to 90 lb/bbl, from 0.1 to 75 lb/bbl, from 0.1 to 50lb/bbl, from 1 to 90 lb/bbl, from 1 to 50 lb/bbl, from 5 to 90 lb/bbl,or from 5 to 50 lb/bbl of the fluid loss additives, the one or moredispersants, or both.

Embodiments of the disclosure also relate to methods of producing thecement slurries previously described. In some embodiments, the methodfor producing a cement slurry may include mixing water with a cementprecursor material and at least one surfactant to produce a cementslurry. As previously described, the surfactant may have the formulaR—(OC₂H₄)_(x)—OH in which R is a hydrocarbyl group having from 10 to 20carbon atoms and x is an integer from 1 to 10. In some embodiments, thesurfactant may have an HLB of from 12 to 13.5. The water, cementprecursor material, and surfactant may be in accordance with any of theembodiments previously described. The cement slurry may include one ormore additives, including but not limited to dispersants and fluid lossadditives. The mixing step, in some embodiments, may involve shearingthe water, cement precursor material, surfactant, and, optionally, otheradditives at a suitable speed for a suitable period of time to form thecement slurry. In one embodiment, the mixing may be done in the labusing a standard API blender. 15 seconds at 4,000 RPM and 35 seconds at12,000 RPM, The equation of mixing energy is:

$\begin{matrix}{\frac{E}{M} = \frac{k\; \omega^{2}t}{V}} & \left( {{Equation}\mspace{14mu} 3} \right)\end{matrix}$

Where

E=Mixing energy (kJ)M=Mass of slurry (kg)k=6.1×10⁻⁸ m⁵/s (constant found experimentally)ω=Rotational speed (radians/s)t=Mixing time (s)V=Slurry volume (m³)

Further embodiments of the present disclosure relate to methods of usingthe cement slurries previously described. In some embodiments, themethod may include pumping the cement slurry into a location to becemented and curing the cement slurry by allowing the water and thecement precursor material to react. The location to be cemented may, forinstance, be a well, a wellbore, an annulus, or other such locations.

Cementing is performed when the cement slurry is deployed into the wellvia pumps, displacing the drilling fluids still located within the well,and replacing them with cement. The cement slurry flows to the bottom ofthe wellbore through the casing, which will eventually be the pipethrough which the hydrocarbons flow to the surface. From there, thecement slurry fills in the space between the casing and the actualwellbore, and hardens. This creates a seal so that outside materialscannot enter the well flow, as well as permanently positions the casingin place. In preparing a well for cementing, it is important toestablish the amount of cement required for the job. This may be done bymeasuring the diameter of the borehole along its depth, using a caliperlog. Utilizing both mechanical and sonic means, multi-finger caliperlogs measure the diameter of the well at numerous locationssimultaneously in order to accommodate for irregularities in thewellbore diameter and determine the volume of the openhole.Additionally, the required physical properties of the cement areessential before commencing cementing operations. The proper set cementis also determined, including the density and viscosity of the material,before actually pumping the cement into the hole.

As used throughout the disclosure, “curing” refers to providing adequatemoisture, temperature and time to allow the concrete to achieve thedesired properties (such as hardness) for its intended use through oneor more reactions between the water and the cement precursor material.In contrast, “drying” refers to merely allowing the concrete to achievea moisture condition appropriate for its intended use, which may onlyinvolve physical state changes, as opposed to chemical reactions. Insome embodiments, curing the cement slurry may refer to passivelyallowing time to pass under suitable conditions upon which the cementslurry may harden or cure through allowing one or more reactions betweenthe water and the cement precursor material. Suitable conditions may beany time, temperature, pressure, humidity, and other appropriateconditions known in the cement industry to cure a cement composition. Insome embodiments, suitable curing conditions may be ambient conditions.Curing may also involve actively hardening or curing the cement slurryby, for instance, introducing a curing agent to the cement slurry,providing heat or air to the cement slurry, manipulating theenvironmental conditions of the cement slurry to facilitate reactionsbetween the water and the cement precursor, a combination of these, orother such means. Usually, the cement will be cured and convert fromliquid to solid due to formation conditions, temperature, and pressure.In the laboratory high temperature and high pressure curing chamber isused for curing the cement specimens at required conditions. Cubicalmolds (2″×2″×2″) and cylindrical cells (1.4″ diameter and 12″ length)were lowered into the curing chamber. Pressures and temperatures weremaintained until shortly before the end of the curing where they werereduced to ambient conditions.

In some embodiments, curing may occur at a relative humidity of greaterthan or equal to 80% in the cement slurry and a temperature of greaterthan or equal to 50° F. for a time period of from 1 to 14 days. Curingmay occur at a relative humidity of from 80% to 100%, such as from 85%to 100%, or 90% to 100%, or from 95% to 100% relative humidity in thecement slurry. The cement slurry may be cured at temperatures of greaterthan or equal to 50° F., such as greater than or equal to 75° F.,greater than or equal to 80° F., greater than or equal to 100° F., orgreater than or equal to 120° F. The cement slurry may be cured attemperatures of from 50° F. to 250° F., or from 50° F. to 200° F., orfrom 50° F. to 150° F., or from 50° F. to 120° F. In some instances, thetemperature may be as high as 500° F. The cement slurry may be cured forfrom 1 day to 14 days, such as from 3 to 14 days, or from 5 to 14 days,or from 7 to 14 days, or from 1 to 3 days, or from 3 to 7 days.

Further embodiments of the present disclosure relate to particularmethods of cementing a casing in a wellbore. The method may includepumping a cement slurry into an annulus between a casing and a wellboreand curing the cement slurry. The cement slurry may be in accordancewith any of the embodiments previously described. Likewise, curing thecement slurry may be in accordance with any of the embodimentspreviously described. As stated above, Cementing is performed when thecement slurry is deployed into the well via pumps, displacing thedrilling fluids still located within the well, and replacing them withcement. The cement slurry flows to the bottom of the wellbore throughthe casing, which will eventually be the pipe through which thehydrocarbons flow to the surface. From there it fills in the spacebetween the casing and the actual wellbore, and hardens. This creates aseal so that outside materials cannot enter the well flow, as well aspermanently positions the casing in place.

Embodiments of the disclosure also relate to methods of producing curedcements. The method may include combining water with a cement precursormaterial, and a surfactant having the formula R—(OC₂H₄)_(x)—OH. Thecement slurry, including the cement precursor material, water, and thesurfactant all may be in accordance with any of the embodimentspreviously described. The method may include curing the cement slurry byallowing for a reaction between the water and the cement precursormaterial to produce cured cement. The curing step may be in accordancewith any of the embodiments previously described.

Embodiments of the disclosure also relate to cured cement compositions.The cured cement may include at least one surfactant having the formulaR—(OC₂H₄)_(x)—OH, in which R is a hydrocarbyl group having from 10 to 20carbon atoms and x is an integer from 1 and 10. The surfactant may be inaccordance with any of the embodiments previous described. Embodimentsof the disclosure are also directed to cured cement compositionscomprising at least one surfactant having an HLB of from 12 to 13.5.

In some embodiments, cement is composed of four main components:tricalcium silicate (Ca₃O₅Si) which contributes to the early strengthdevelopment; dicalcium silicate (Ca₂SiO₄), which contributes to thefinal strength, tricalcium aluminate (Ca₃Al₂O₆), which contributes tothe early strength; and tetracalcium alumina ferrite. These phases aresometimes called alite and belite respectively. In addition, gypsum isadded to control the setting time of cement.

In one embodiment, the silicates phase in cement may be about 75-80% ofthe total material. Ca₃O₅Si is the major constituent, with concentrationas high as 60-65%. The quantity of Ca₂SiO₄normally does not exceed 20%(except for retarded cements). The hydration products for Ca₃O₅Si andCa₂SiO₄ are calcium silicate hydrate (Ca₂H₂O₅Si) and calcium hydroxide(Ca(OH)₂), also known as Portlandite. The calcium silicate hydratecommonly called CSH gel has a variable C:S and H:S ratio depending onthe temperature, Calcium concentration in the aqueous phase, and thecuring time. The CSH gel comprises +/−70% of fully hydrated Portlandcement at ambient conditions and is considered the principal binder ofhardened cement. By contrast, the calcium hydroxide is highlycrystalline with concentration of about 15-20 wt. % and is the reasonfor the high pH of cement. Upon contact with water, the gypsum maypartially dissolves releasing calcium and sulphate ions to react withthe aluminate and hydroxyl ions produced by the C3A to form a calciumtrisulphoaluminate hydrate, known as the mineral Ettringite(Ca₆Al₂(SO₄)₃(OH)₁₂.26H₂O) that will precipitate onto the Ca₃O₅Sisurfaces preventing further rapid hydration (flash-set). The gypsum isgradually consumed and ettringite continues to precipitate until thegypsum is consumed. The sulphates ion concentration will be drop downand the ettringite will become unstable converting to calciummonosulphoaluminate hydrate (Ca₄Al₂O₆(SO₄).14H₂O). The remainingunhydrated Ca₃O₅Si will form calcium aluminate hydrate. Cement slurrydesign is based on the altering or inhibition of the hydration reactionswith specific additives.

The cured cement may include one or more of calcium hydroxide,silicates, oxides, belite (Ca₂SiO₅), alite (Ca₃SiO₄), tricalciumaluminate (Ca₃Al₂O₆), tetracalcium aluminoferrite (Ca₄Al₂Fe₂O₁₀),brownmillerite (4CaO.Al₂O₃.Fe₂O₃), gypsum (CaSO₄.2H₂O) sodium oxide,potassium oxide, limestone, lime (calcium oxide), hexavalent chromium,calcium aluminate, other similar compounds, and combinations of these.The cement precursor material may include Portland cement, siliceous flyash, calcareous fly ash, slag cement, silica fume, any known cementprecursor material or combinations of any of these.

The cured cement may contain from 0.1 to 10% BWOC of the at least onesurfactant based on the total weight of the cured cement. For instance,the cured cement may contain from 0.1 to 8% BWOC of the surfactant, orfrom 0.1 to 5% BWOC of the surfactant, or from 0.1 to 3% BWOC of thesurfactant. The cured cement may contain from 1 to 10% BWOC of thesurfactant, from 1 to 8% BWOC, from 1 to 5% BWOC, or from 1 to 3% BWOCof the surfactant. In some embodiments, the cured cement may containfrom 3 to 5% BWOC, from 3 to 8% BWOC, from 3 to 10% BWOC, or from 5 to10% BWOC of the surfactant.

The cured cement may contain from 0.1 to 10% BWOC of one or moreadditives based on the total weight of the cured cement. The one or moreadditives may include accelerators, retarders, extenders, weightingagents, fluid loss control agents, lost circulation control agents,other surfactants, antifoaming agents, specialty additives, andcombinations of these. For instance, the cured cement may contain from0.1 to 8% BWOC of the one or more additives, or from 0.1% BWOC to 5%BWOC of the one or more additives, or from 0.1 to 3% BWOC of the one ormore additives. The cured cement may contain from 1 to 10% BWOC of theone or more additives, or from 1 to 8% BWOC, or from 1 to 5% BWOC, orfrom 1 to 3% BWOC of the one or more additives. In some embodiments, thecured cement may contain from 3 to 5% BWOC, or from 3 to 8% BWOC, orfrom 3 to 10% BWOC, or from 5 to 10% BWOC of the one or more additives.

Without being bound by any particular theory, controlling the fluid lossand rheology properties of the cement slurry when producing the curedcement may result in a stronger, more stable cured cement, as previouslydiscussed. In some embodiments, the cured cement of the presentdisclosure may have a compressive strength of from 400 to 5000 psi. inthe compressive Strength Test. In the test, the set cement cubes wereremoved from the molds, and placed in a hydraulic press where increasingforce was exerted on each cubes until failure. The hydraulic presssystem used in this study applied known compressive loads to thesamples. This system was designed to test the compressive strength ofsample cement cubes in compliance with API specifications for oil wellscement testing.

Similarly, the cured cement produced may have a higher density thanconventional cements, which may not cure as uniformly, due to the issuespreviously described, such as rheology and fluid loss. In someembodiments, the cured cement may have a density of from 70 pounds percubic foot (lb/f³) to 160 lb/f³.

The cured cement composition may have improved wettability properties.Wettability refers to the tendency for fluid to spread out on or adhereto a solid surface in the presence of other immiscible fluids. Withoutbeing bound by any particular theory, cement slurries and cured cementcompositions having high wettability may reduce the risk of cementcontamination and bonding problems to ensure a strong bong as the cementslurry is cured or dried into cured cement. This may produce a strongerannular seal between the annulus and the cured cement, as previouslydescribed.

In some embodiments, the cement slurry may contain water and may bewater-based. As such, the cement slurry may by hydrophilic, formingstronger bonds with water-wet surfaces. Well sections drilled withnon-aqueous drilling fluids may have oil-wet surfaces, resulting in poorbonding between the well and the cement slurry, as oil and waternaturally repel. Poor bonding may lead to poor isolation and a buildupof unwanted casing-casing or tubing-casing annular pressure. In someembodiments, the addition of the alcohol surfactant to the cementslurry, the cured cement composition, or both, may address thesedifficulties to provide a better bond by rendering the well surface morewater wet. Without being bound by theory, it is desirable to make theformation or/and casing water wet to enhance and improve the bondingbetween cement and casing and cement and formation. If the wettabilityof the formation or casing is oil wet not water wet then the bondingwill be poor and could result in small gap(s) or channel(s) between thecement and casing or the cement and formation thereby resulting inimproper wellbore isolation. This improper wellbore isolation could leadto fluid or gas escaping from the well through this gas or channel dueto de-bonding.

As a non-limiting example, to perform a wettability test, casing couponsused in the test may be a piece of metal taken as a sample from thetubulars that will be cemented downhole. A piece of Teflon tape may beplaced down the center of the casing coupon to provide a standard for acomplete oil-wet surface To the left of the Teflon tape strip, thecasing metal coupon is present while the side to the right of the tapeis left unwashed. The washing is performed using surfactant. The side ofcasing coupon is washed in a viscometer cup filled with the specifiedsurfactant solution. The viscometer is rotated at 100 RPM for 30 min andat a temperature of 140° F. A water droplet may be placed in each of thethree sections. The droplet may be visually observed after a period oftime, after undergoing a variety of conditions, or after a combinationof both to determine the wettability. The same test procedure may beperformed with a piece of cured cement composition in place of thecasing coupon metal.

The droplet on the Teflon surface may not absorb into the cement butrather may maintain a contact angle with the test surface of from 120°to 180°. The droplet on the Teflon surface should consistently displaypoor wettability and can be used as a control sample. To the left andright of the Teflon strip, the water droplet may completely absorb intothe cement, partially absorb into the cement, may spread out onto thecured cement, or may maintain its spherical droplet nature based on howwater-wet the cement is. In some embodiments, a droplet having a contactangle of greater than 90° may be considered cement having poor waterwettability. A droplet having a contact angle of less than 90° butgreater than or equal to 35° may be considered cement having fairwettability. Finally, if the droplet has a contact angle of less than35° the cement may have good wettability. Water wettability may beinversely related to oil wettability. That is, if a water droplet isrepelled by the cement, it may be an indication that the cement ishydrophobic and may have good oil-wettability, or an affinity for oil.

As mentioned, the droplet may be observed under a variety of conditions.In some embodiments, the wettability of the cured cement, and/or thewettability of the casing coupon may be observed after preheating thecement for 30 minutes at a temperature of 140° F. Likewise, the cementmay be immersed in an oil based mud for 10 minutes and the wettabilitymay be observed. In some embodiments, the cement may be attached to arotor or a viscometer cup and may be immersed in a spacer fluid suchthat at least about two thirds of the cement is immersed in the fluid.The cement is immersed while being attached to a side of viscometer cupto insure it remains static while the fluid is being stirred by theviscometer rotation The cement may be rotated at 100 rotations perminute (RPMs) for 30 minutes and the wettability determined. Theintention of dipping the sample in oil based mud is to insure that thesample is “oil-wet”. Oil wet samples will show a specific contact anglewith water (<90°). After that, the same sample may dipped in surfactantto try and convert it to being “water-wet”. Water wet samples will showa different contact angle (>90°). If the surfactant is successful, itwill be able to convert the sample into being a water-wet and this willbe shown from the contact angle variations.

EXAMPLES

Rheology testing was conducted on various formulations of the cementslurry of the present embodiments as compared to conventional cementslurries. Notably, in some embodiments, the cement slurry of the presentdisclosure may have a viscosity as measured using a Fann 35 rheometeraccording to American Petroleum Institute Specification RP 13B at 600rotations per minute (RPM) of less than 100 after 10 minutes. In someembodiments, the cement slurry may have a rheology reading at 600 RPM ofless than or equal to 95, such as less than or equal to 90 after 10minutes. In some embodiments, the cement slurry may have a viscosity at600 RPM of from 75 to 100, or 75 to 95, or 80 to 95, or 80 to 90, or 80to 100, or 85 to 100, after 10 minutes. In some embodiments, the cementslurry may have a viscosity at 300 RPM of less than or equal to 60, suchas less than or equal to 55 after 10 minutes. In some embodiments, thecement slurry may have a viscosity at 300 RPM of from 50 to 75, or 55 to75, or 50 to 65, or 50 to 60, or 50 to 55 after 10 minutes. In someembodiments, the cement slurry may have a viscosity at 200 RPM of lessthan or equal to 60, such as less than or equal to 55, or less than orequal to 50, or less than or equal to 45 after 10 minutes. In someembodiments, the cement slurry may have a viscosity at 200 RPM of from40 to 65, or 45 to 65, or 40 to 55, or 40 to 50, or 45 to 50 after 10minutes. In some embodiments, the cement slurry may have a viscosity at100 RPM of less than or equal to 50, such as less than or equal to 40,or less than or equal to 35, or less 10 minutes. In some embodiments,the cement slurry may have a viscosity at 6 RPM of less than or equal to15, such as from 10 to 15 after 10 minutes. In some embodiments, thecement slurry may have a viscosity at 3 RPM of less than or equal to 10,such as less than or equal to 8 after 10 minutes.

Fann Model 35 viscometers are used in research and production. Theseviscometers are recommended for evaluating the rheological properties offluids, Newtonian and non-Newtonian. The design includes a R1 RotorSleeve, B1 Bob, F1 Torsion Spring, and a stainless steel sample cup fortesting according to American Petroleum Institute Recommended Practicefor Field Testing Water Based Drilling Fluids, API RP 13B-1/ISO 10414-1Specification. The test fluid is contained in the annular space or sheargap between the cylinders. Rotation of the outer cylinder at knownvelocities is accomplished through precision gearing. The viscous dragexerted by the fluid creates a torque on the inner cylinder or bob. Thistorque is transmitted to a precision spring where its deflection ismeasured and then related to the test conditions and instrumentconstants. This system permits the true simulation of most significantflow process conditions encountered in industrial processing. DirectIndicating Viscometers combine accuracy with simplicity of design, andare recommended for evaluating materials that are Bingham plastics.Model 35 Viscometers are equipped with factory installed R1 RotorSleeve, B1 Bob, F1 Torsion Spring, and a stainless steel sample cup fortesting according to American Petroleum Institute Specification RP 13B.Other rotor-bob combinations and/or torsion springs can be substitutedto extend the torque measuring range or to increase the sensitivity ofthe torque measurement. Shear stress is read directly from a calibratedscale. Plastic viscosity and yield point of a fluid can be determinedeasily by making two simple subtractions from the observed data when theinstrument is used with the R1-B1 combination and the standard F1torsion spring.

In some embodiments the cement slurry may have a viscosity at 600 RPM ofless than 150, or less than 130, or less than 125, or less than 120after 30 minutes. In some embodiments, the cement slurry may have aviscosity at 300 RPM of less than or equal to 100, such as less than orequal to 90, such as less than or equal to 80 after 30 minutes. Thecement slurry may have a viscosity at 200 RPM of less than or equal to75, such as less than or equal to 70, or less than or equal to 65 after30 minutes. The cement slurry may have a viscosity at 100 RPM of lessthan or equal to 60, such as less than or equal to 55, or less than orequal to 50 after 30 minutes. In some embodiments, the cement slurry mayhave a viscosity at 6 RPM of less than or equal to 15, or less than orequal to 12, such as from 10 to 15 after 30 minutes. In someembodiments, the cement slurry may have a viscosity at 3 RPM of lessthan or equal to 10, such as less than or equal to 8 after 30 minutes.

In some embodiments the cement slurry may have a viscosity at 600 RPM ofless than 210, or less than 205, or less than 200 after 90 minutes. Insome embodiments, the cement slurry may have a viscosity at 300 RPM ofless than or equal to 150, such as less than or equal to 140, such asless than or equal to 130, such as less than or equal to 125 after 90minutes. The cement slurry may have a viscosity at 200 RPM of less thanor equal to 120, such as less than or equal to 110, or less than orequal to 100 after 90 minutes. The cement slurry may have a viscosity at100 RPM of less than or equal to 100, such as less than or equal to 95,or less than or equal to 90, or less than or equal to 85 after 90minutes. In some embodiments, the cement slurry may have a viscosity at6 RPM of less than or equal to 20, or less than or equal to 15, or lessthan or equal to 12, such as from 10 to 15 after 90 minutes. In someembodiments, the cement slurry may have a viscosity at 3 RPM of lessthan or equal to 12, such as less than or equal to 10, or less than orequal to 8 after 90 minutes.

TABLE 1 Sample Compositions Sample Composition Example 1 353 cubiccentimeters (cc) distilled water 2 grams (g) synthetic branchedisotridecyl alcohol shown below.  

  1 g retarder calcium lignosulfonate 800 g Portland Class G CementComparative 353 cc distilled water Example 1 800 g Portland Class GCement Comparative 353 cc distilled water Example 2 1 g retarder 800 gPortland Class G Cement Comparative 353 cc distilled water Example 3 2 gmono-ethanolamine 800 g Portland Class G Cement Comparative 353 ccdistilled water Example 4 1 g retarder 2 g mono-ethanolamine 800 gPortland Class G Cement

Table 1 lists the compositions of each cement slurry sample tested.Example 1 is a cement slurry in accordance with the present disclosure.Example 1 contains 353 cubic centimeters (cc) of water as the water, 800grams (g) cement as the cement precursor material, 2 g of syntheticbranched isotridecyl alcohol as the at least one surfactant, and anadditional additive of 1 g retarder. Comparative Example 1 is a cementslurry containing only water and cement without the surfactant orretarder. Comparative Example 2 is a cement slurry containing water,cement, and 1 g retarder, but no surfactant. Comparative Example 3contains water, cement, and 2 g mono-ethanolamine as a surfactant thatis not in accordance with embodiments of the present disclosure (as thesurfactant does not include a compound with the formula R—(OC₂H₄)_(x)—OHwhere R is a hydrocarbyl group with 10 to 20 carbons and x is an integerfrom 1 to 10). Finally, Comparative Example 4 similar to Example 1 ofthe present disclosure as it contains cement, water, a retarder, and asurfactant, but again, mono-ethanolamine is used as the surfactant.

The viscosity of each sample was determined over various time intervalsand various RPMs using a Fann 35 rheometer in accordance with API RP13B-1/ISO 10414-1 Specifications. The Fann 35 rheometer has a dialreading scale up to 300, thus, “out of 300” refers to a viscosity over300 that is too viscous to be measured on the rheometer scale.Similarly, “gelled” refers to a composition so viscous that it formed agel.

TABLE 2 Rheology Reading after 10 Minutes of Elapsed Time Sample Tested600 RPM 300 RPM 200 RPM 100 RPM 6 RPM 3 RPM Example 1 88 56 45 34 13 7Comparative 156 119 104 87 12 10 Example 1 Comparative 100 68.5 57 43.511 8 Example 2 Comparative 151 125 104 82 19 13 Example 3 Comparative140 100 88 68 15 10 Example 4

TABLE 3 Rheology Reading after 30 Minutes of Elapsed Time Sample Tested600 RPM 300 RPM 200 RPM 100 RPM 6 RPM 3 RPM Example 1 120 78 67 51 12 8Comparative Out of 300 281 243 169 17 13 Example 1 Comparative 170 12294 68 14 9 Example 2 Comparative 156 125 110 91 13 11 Example 3Comparative 234 176 140 88 12 8 Example 4

TABLE 4 Rheology Reading after 90 Minutes of Elapsed Time Sample Tested600 RPM 300 RPM 200 RPM 100 RPM 6 RPM 3 RPM Example 1 206 128 110  86 1510 Comparative Gelled Gelled Gelled Gelled Gelled Gelled Example 1Comparative Out of 300 265 234 182 75 75 Example 2 Comparative GelledGelled Gelled Gelled Gelled Gelled Example 3 Comparative Gelled GelledGelled Gelled Gelled Gelled Example 4

As shown in Tables 2 to 4, Example 1 of the present embodiments showedsuperior rheology as compared to Comparative Examples 1-4. As shown inTables 2 to 4, the viscosity of Example 1 is less than any of thecomparative examples, including Comparative Example 4. Having a lowviscosity may allow the cement slurry to be more easily and moreprecisely positioned, for instance, in an oil or gas well. Notably,under all conditions tested, Example 1 did not gel, even after 90minutes of elapsed time at 600 to 3 RPM. When a cement slurry gels itmay become quite difficult to handle and place the slurry, which may berendered unpumpable and may be difficult to remove.

The following description of the embodiments is illustrative in natureand is in no way intended to be limiting it its application or use. Asused throughout this disclosure, the singular forms “a,” “an” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a” component includes aspects havingtwo or more such components, unless the context clearly indicatesotherwise.

It should be apparent to those skilled in the art that variousmodifications and variations may be made to the embodiments describedwithin without departing from the spirit and scope of the claimedsubject matter. Thus, it is intended that the specification cover themodifications and variations of the various embodiments described withinprovided such modification and variations come within the scope of theappended claims and their equivalents.

It is noted that one or more of the following claims utilize the term“where” as a transitional phrase. For the purposes of defining thepresent technology, it is noted that this term is introduced in theclaims as an open-ended transitional phrase that is used to introduce arecitation of a series of characteristics of the structure and should beinterpreted in like manner as the more commonly used open-ended preambleterm “comprising.”

Having described the subject matter of the present disclosure in detailand by reference to specific embodiments of any of these, it is notedthat the various details disclosed within should not be taken to implythat these details relate to elements that are essential components ofthe various embodiments described within, even in cases where aparticular element is illustrated in each of the drawings that accompanythe present description. Further, it should be apparent thatmodifications and variations are possible without departing from thescope of the present disclosure, including, but not limited to,embodiments defined in the appended claims. More specifically, althoughsome aspects of the present disclosure are identified as particularlyadvantageous, it is contemplated that the present disclosure is notnecessarily limited to these aspects.

What is claimed is:
 1. A cement slurry comprising: water; a cementprecursor material; and a surfactant having a HLB of from 12 to 13.5. 2.The cement slurry of claim 1, where the cement slurry contains from 10to 70 wt % BWOC (By Weight Of Cement Precursor) water.
 3. The cementslurry of claim 1, where the cement slurry contains from 10 to 90 wt %BWOC of the cement precursor material.
 4. The cement slurry of claim 1,where the cement slurry contains from 0.1 to 10 wt % BWOC of thesurfactant.
 5. The cement slurry of claim 1, where the cement slurrycontains from 0.1 to 10 wt % BWOC of one or more additives selected fromthe group consisting of accelerators, retarders, extenders, weightingagents, fluid loss control agents, lost circulation control agents,antifoaming agents, and combinations of these.
 6. The cement slurry ofclaim 1, where the cement precursor material is a hydraulic or anon-hydraulic cement precursor.
 7. The cement slurry of claim 1, wherethe cement precursor material is a hydraulic cement precursor.
 8. Thecement slurry of claim 1, where the cement precursor material comprisesone or more components selected from the group consisting of calciumhydroxide, silicates, belite (Ca₂SiO₅), alite (Ca₃SiO₄), tricalciumaluminate (Ca₃Al₂O₆), tetracalcium aluminoferrite (Ca₄Al₂Fe₂O₁₀),brownmillerite (4CaO.Al₂O₃.Fe₂O₃), gypsum (CaSO₄.2H₂O), lime (calciumoxide), calcium aluminate, and combinations thereof.
 9. The cementslurry of claim 1, where the cement precursor material comprisesPortland cement precursor, siliceous fly ash, calcareous fly ash, slagcement, or combinations thereof.
 10. The cement slurry of claim 1, wherethe cement precursor material comprises Portland cement precursor. 11.The cement slurry of claim 1, where the HLB is from 12.5 to
 13. 12. Thecement slurry of claim 1, where the surfactant comprises anaturally-derived fatty alcohol or a synthetically-derived fattyalcohol.
 13. The cement slurry of claim 1, where the surfactantcomprises ethylene oxide condensate of branched isotridecyl alcohol.